Liquid crystal display (LCD) is commonly used as a display device because of its capability of displaying images with good quality while using little power. An LCD apparatus includes an LCD panel formed with liquid crystal cells and pixel elements with each associating with a corresponding liquid crystal cell and having a liquid crystal capacitor and a storage capacitor, a thin film transistor (TFT) electrically coupled with the liquid crystal capacitor and the storage capacitor. These pixel elements are substantially arranged in the form of a matrix having a number of pixel rows and a number of pixel columns. Typically, scanning signals are sequentially applied to the number of pixel rows, through a plurality of scanning lines along the row direction, for sequentially turning on the pixel elements row-by-row. When a scanning signal is applied to a pixel row to turn on corresponding TFTs of the pixel elements of a pixel row, source signals (image signals) for the pixel row are simultaneously applied to the number of pixel columns, through a plurality of data lines arranged crossing over the plurality of scanning lines along the column direction, so as to charge the corresponding liquid crystal capacitor and storage capacitor of the pixel row for aligning orientations of the corresponding liquid crystal cells associated with the pixel row to control light transmittance therethrough. By repeating the procedure for all pixel rows, all pixel elements are supplied with corresponding source signals of the image signal, thereby displaying the image signal thereon.
Occasionally, manufacturing defects may occur in an LCD panel. The defects include, (1) one or more scanning lines are broken, (2) one or more data lines are broken, and (3) one or more scanning lines are short circuited with one or more data lines. A defect on a scanning or data line can adversely affect overall performance of the LCD device. For example, if an open circuit condition occurs in a LCD panel, the active components connected to the line beyond the point where the open circuit exists is disabled. A short circuit between a data and a scanning line can also lead to inaccurate signals being applied to all switching transistors connected to either of the shorted data or scanning lines. In either case, multiple pixels in the device can be affected, thereby significantly diminishing its display quality. A device having such defective scanning lines or data lines may have to be discarded, depending upon the degradation of the resolution of the display device resulting from the inoperative pixels resulting.
Given the expense of fabricating LCD devices, it is desirable to have devices that are repairable after they have been assembled. In one common approach, a thin film display device has a plurality of auxiliary conductive lines disposed across the scanning lines or data lines on the sides of the device, usually, outside the active areas of the device.
U.S. Pat. No. 5,086,347 to Ukai et al. discloses a repair method for an LCD device. As shown in FIG. 1, a plurality of repair conductive layers 41 is provided opposite of a scanning lines 18 across an insulating layer (not shown), and a plurality of repair conductive layer 42 is provided opposite of a data line 19 across the insulating layer (not shown). When any one of the scanning lines or data lines is broken, a repair conductive layer and the broken line can be connected by at both side of the broken portion by laser welding, where the welding points are indicated as “x” in FIG. 1. The problem with this method is that once a conductive layer is used to repair a given line, however, it cannot be used for repairing of any other lines. Moreover, if one or more scanning lines or data lines are open at a crossover of a scanning line and a data line, this type of the defects may not be repaired using the method. Additionally, due to the special relation of the conductive repair layers 41, and 42 and the scanning line 18 and the data line 19, parasitic capacitances may be induced by the conductive repair layers 41, and 42. A parasitic capacitance may cause a DC voltage offset to an AC voltage applied to liquid crystal layer, thereby generating flicker, crosstalk, and non-uniformity of luminance in the images.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.